Aromatic esters of dimer acid

ABSTRACT

BENZYL ESTERS OF DIMERIZED LINOLEIC ACID AND HYDROGENATED DIMERIZED LINOLEIC ACID WERE PREPARED BY RACTING THE DIMER ACID WITH THE APPROPRIATE ALCOHOL IN THE PRESENCE OF AN ACID CATALYST. THE ESTERS WERE EVALUATED AND FOUND TO HAVE VICOSITY CHARACTERISTICS, LUBRICATING PROPERTIES AND THERMAL STABLITIES DESIRED N LUBRICANTS, LUBRICANT ADDITIVES AND HYDRAULIC FLUIDS.

United States Patent Ofice US. Cl. 260-407 9 Claims ABSTRACT OF THE DISCLOSURE Benzyl esters of dimerized linoleic acid and hydrogenated dimerized linoleic acid were prepared by reacting the dimer acid with the appropriate alcohol in the presence of an acid catalyst. The esters were evaluated and found to have viscosity characteristics, lubricating properties and thermal stabilities desired in lubricants, lubricant additives and hydraulic fluids.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sub-licenses for such purposes, is hereby granted to the Government of the United States of America.

This application is a division of Ser. No. 433,524, filed Feb. 17, 1965, now US. Pat. No. 3,393,214.

This invention relates to *benzyl and substituted benzyl esters of dimer (dilinoleic) acid and has among its objects the preparation of fluids of high thermal stability for use as lubricants, lubricant additives and hydraulic fluids.

Modern industry has an increasing need for superior lubricants for use in equipment designed to operate over a great temperature dilferential. There are many lubricant problems which cannot be solved by the use of mineral hydrocarbon lubricating oils. Synthetic materials previously prepared and used as specialty lubricants include the compounds bis(2-ethylhexyl) sebacate and dibenzyl sebacate employed as controls for evaluating the compounds of the present invention. These sebacate esters have many desirable properties, but compounds of greater thermal stability are needed.

The compounds of the present invention may be represented by the formula .wherein R is a dia'cyl radical derived from dirnerized linoleic acid or the hydrogenated product thereof and, when X is hydrogen, A may be hydrogen, a short carbon chain alkoxy group, a straight or branched chain low molecular weight alkyl group, or the nitro group. When X is a phenyl group, A is hydrogen.

Representative compounds were prepared, characterized, and evaluated for usefulness. In general, the compounds of the present invention have favorable viscosity characteristics and are equal to or better than the sebacate ester controls in regard to lubricating properties as indicated by the wear scar test. Most of the present compounds have excellent thermal stability; onset of decomposition for several being in the range of about 370390 C. as compared to about 290-300 C. for the controls.

Among the preferred compounds are those in which A is hydrogen or an alkyl group. The highest thermal stabilities were exhibited by bis(benzyl)-dilinoleate and the corresponding ester of the hydrogenated dimer, called 3,555,057 Patented Jan. 12, 1971 hydrogenated bis(benzyl)-dilinoleate. An alkyl group at A is typified with the isopropyl radical, the compound being designated bis(p-isopropylbenzyl)-dilinoleate, but it is readily apparent that other alkyl groups such as methyl, ethyl, propyl, butyl and isobutyl provide esters of high thermal stability. A compound in which A is an alkoxy group, as in the methoxy derivative, bis(anisyl)-dilinoleate, has high thermal stability and is both a viscositytemperature improver and wear improver for base oils. The alkoxy group may also be ethoxy, propoxy or isopro poxy. The presence of a nitro group at A is exemplified with bis(p-nitrobenzyl)-dilino1eate. An aryl group at X is demonstrated with a phenyl group in bis(benzhydryl)- dilinoleate.

In a typical procedure for preparation of the esters a ratio of two moles alcohol to one mole dimer acid and a small amount of an acid catalyst were dissolved in an inert organic solvent such as benzene and refluxed until the reaction was. complete, as indicated by amount of water collected. The benzene solution was washed until free of acid, dried over calcium sulfate, the benzene removed, and the crude product purified by molecular distillation. We have found that the dilinoleate esters of the present invention are liquids, even though total molecular weightof a compound is as high as about 900.

The dimer acid employed in the preparation of the esters contained 95% dilinoleic acid, 4% trimer acid and 1% monobasic acid and had characteristics of acid number, 191.2; neutralization equivalent, 293.4; and molecular weight, 565. The hydrogenated dimer acid had an acid number of 192.8; neutralization equivalent, 288.0;

and iodine number 29.0. The alcohols were commercial products and only the anisyl alcohol was redistilled before use. Best results were obtained with use of naphthalene-2-sulfonic acid as the catalyst. Naphthalene-l-sulfonic acid, methane sulfonic acid and sulfuric acid gave poorer results than naphthalene-2-sulfonic acid.

Preparation of the esters of the invention is illustrated by the following examples:

EXAMPLE 1 Dimer acid, 149 g.; benzyl alcohol, 58 g.; and 3 g. naphthalene-Z-sulfouic acid were combined with 200 ml. benzene in a one-liter 3-neck flask. The flask was equipped with a thermometer, a magnetic stirrer, and a Dean and Stark tube: with a water cooled condenser. The mixture was heated at 90 C. reflux temperature until the calculated amount of water (9.5 ml.) was separated; reaction time 3 hours. After cooling the reaction mixture was washed until acid-free. The benzene solution was dried over calcium sulfate, filtered, and the benzene evaporated under vacuum. The crude product, an amber fluid, weighed 189 g., a yield of 95%. The product has an acid No. of zero, and infrared spectra indicated absence of acid and presence of ester carbonyl. The crude product was purified by molecular distillation, the main fraction being collected between 280- 300 C. at 9 to 15 microns pressure. This function weighed 156.2 g. and had a molecular weight of 750.

EXAMPLE 2 The process of Example 1 was repeated except that 151 g. of hydrogenated dimer acid was used in place of the dimer and the mixture was refluxed 4 hours. Yield of crude ester was 90.4%.

EXAMPLE 3 Following the typical procedure, 282.5 g. dimer acid, 150.2 g. p-isopropyl benzyl alcohol and 5.65 g. naphthalene-2-sulfonic acid were refluxed for 5 hours and the crude bis(p-isopropylbenzyl)-dilinoleate was separated from the reaction mixture in 99% yield. The product was purified by molecular distillation.

EXAMPLE 4 In a procedure similar to previous examples, dimer acid, 28.3 g.; benzhydryl alcohol (a-phenylbenzyl alcohol) 18.3 g.; and 0.65 g. catalyst were refluxed 8 hours, the crude ester separated from the reaction mixture in 90% yield and the bis(benzhydryl)-dilinoleate purified by molecular distillation.

EXAMPLE 5 Dimer acid, 45.6 g.; p-nitrobenzyl alcohol, 25.0 g.; and 1.82 g. of naphthalene-Z-sulfonic acid were combined in benzene solution and refluxed 8 hours, the crude ester separated from the reaction mixture (90% yield) and the bis(p-nitrobenzyl)-dilinoleate purified by molecular distillation.

EXAMPLE 6 Dimer acid, 10.2 g.; anisyl alcohol, 5.0 g.; and 0.4 g. catalyst were combined in benzene and refluxed 6 hours, the crude ester separated as described in Example 1 and bis(anisyl)-dilinol.eate purified by molecular distillation. Yield was 80%.

EXAMPLE 7 As a control material, dibenzyl sebacate was prepared from sebacic acid and benzyl alcohol. The typical procedure for preparation of esters was followed.

Physical and chemical data pertaining to the compounds of the examples were determined. Some of the data are presented in Table I.

Among the evaluations for usefulness of the compounds of the present invention were properties of thermal stability, viscosity characteristics and lubrication as indi- 1 The sample holder was made from 4 mm. Pyrex glass tubing, 24 cm. long. A small bulb (capacity-approximately 0.5 ml., 1.0 cm. diameter was formed at one end of the tube and a flared lip was formed at the other. The size of the bulb may be varied for the weight of the sample being used. The bulb, with the above dimensions, will accommodate a sample weighing 100 mg. The sample was placed in the holder with a long, thin dropper, being careful not to deposit liquid on the wall of the tube. The holder was then attached to the eyelet of the weighting mechanism (support rod) with a hook made from 22 gauge Nichrome wire. Using this arrangement, the sample holder tube extends approximately 7.5 cm. above the top of the furnace while the bulb is located approximately 6 mm. above the sample thermocouple well. This distance can be adjusted by the wire hook.

The samples were heated to 525-575 C. at a heating rate of 3 C. per minute in a dry air atmosphere which flowed at a rate of 10 ml. per minute at atmospheric pressure. Decomposition took place at a maximum of onethird of the distance up the sample holder tube as evidenced by observation of carbonaceous matter. Onset of decomposition is defined as the point where (a) the material shows the first detectable weight loss as determined by a deviation from a blank run and/or (b) the slope, dw/dT shows a radical change from some minimum value.

The viscosity index was determined according to the procedure given in ASTM D567-53, using semi-micro viscometers.

Lubricating property was evaluated using the four ball wear test as described by Peale et al., Lubrication Eng.

Trans. 3, 48 (1960).

In the wear test, the smaller value denotes the best lubricating property. Several of the compounds were noticeably superior to the controls and the remainder compared favorably.

We claim:

1. An ester of the formula H wherein R is selected from the group consisting of the diacyl radical of dimerized linoleic acid and the diacyl TABLE I.CHARACTERISTICS OF DILINOLEATE ESTERS AND SEBACATE CONTROL Saponifieation Saponification B P 1 Carbon, percent Hydrogen, percent number equivalent Calcu- Calcu- Caleu- Calcu- Example No. Compounds C. Mlcrons ND Iated Found 2 Iated Found lated Found lated Found 1 B1S(bellZyl)-dlll1l0l0fili8.. 280 9 1. 5028 81. 03 81. 11 10.35 10. 54 151. 4 146. 4 270. 6 383. 2 Hgdlrogenatted b1s(benzyl)- 275 10 1. 5013 80. 59 80. 68 10. 52 10.56 150. 6 147. 0 371. 8 381. 5

1 mo ea e. Biggp-ispprtopylbenzyb- 300 10 1. 5020 81. 80. 10. 74 10. 84 136. 0 138. 3 412. 7 406. 0

1 mo ea c. Bistbenzhydryl)-dilinoleate 1. 5295 83. 36 82. 72 9. 48 9. 53 125. 6 126. 2 446. 8 444. 6 5 B1S(p-n1trobenzyl)- 200 10 1. 5177 72. 25 72. 33 8. 98 9. 32 135. 0 139. 5 415. 6 403. 0

dilinoleate. 6 Bis(anisyl)-di1inoleate 225 6 1. 5230 77. 95 77. 80 10. 06 9. 60 140. 1 143. 5 400. 6 391. 0 7 Dibenzyl sebaeate 5 180 7 a 1. 5162 75. 36 76. 49 7. 91 8.03

1 1\Iolecularly distilled.

2 Based on ealcd. molecular Weight of dilinoleic acid (MW. 561), not on molecular Weight derived from commercial dimer acid (MW. 565).

3 Alcohol insol. fraction.

4 Nitrogen, ealed. 3.37; found, 3.12. 5 Control sample.

Solid at room temperature.

TABLE IL-THE RMAL STABILITY, VISCOSITY, AND LUBRICA'IING PROPERTIES OF DILINOLEATE ESTERS AND CONTROLS Onset of decomposition Wear scar temperature Viscosity diameter Sample C. 1 index mm.

Example No.:

l Bis(benzyl) 384 124. 3 0.653 2 Hydrogenated b1s(benzyl).- 392 126. 0 0. 748 3. Bis(p-1sopropylbenzyl) 368 110. 2 0. 843 4 B s(benz lydryl) 306 78. 4 0.829 5 B1s(p-nitrobenzyl) 273 95. 4 0.863 G Bis(anisyl) 345 0. 473 Bis(2-ethy1hexyl)sebaeate 289 148. 8 0. 830 7 Dibenzyl sebaeate 300 0. 950 100 paratlin oil 112. 7 0.803

1 Temperatures determined on average of 3 runs. Acculaev, i=4".

radical of hydrogenated dimerized linoleic acid and A is se- 8. An ester of claim 1 in which R is the diacyl radical lected from the group consisting of hydrogen, methyl, of hydrogenated dimerized linoleic acid.. ethyl, propyl, isopropyl, butyl, isobutyl, nitro, and a short 9. The ester of claim 8 in which A is hydrogen.

carbon chain alkoxy group.

2. An ester of claim 1 in which R is the diacyl radical References Cited of dimerized linoleic acid. UNITED ES PATENTS 3. The ester of claim 2 in which A is hydrogen. 4. The ester of claim 2 in which A is isopropyl. g l I 353; 5. The ester of claim 2 in which A is nitro. at er et a n 6. An ester of claim 2 in which A is a short carbon 10 LORRAINE A WEINBERGER Primar Examiner chain alkoxy group. Y

7. The ester of claim 6 in which A is methoxy. R. S. WEISSBERG, Assistant Examiner 

